LuxSensor.ino

/*
  Vera Arduino BH1750FVI Light sensor
  communicate using I2C Protocol
  this library enable 2 slave device addresses
  Main address  0x23
  secondary address 0x5C
  connect the sensor as follows :

  VCC  >>> 5V
  Gnd  >>> Gnd
  ADDR >>> NC or GND  
  SCL  >>> A5
  SDA  >>> A4
  
  Contribution: idefix
 
*/

#include <SPI.h>
#include <MySensor.h>  
#include <BH1750.h>
#include <Wire.h> 

#define CHILD_ID_LIGHT 0
#define LIGHT_SENSOR_LUX_THRESHOLD 20 // only if lastlux higher as lux+-threshold send a message
unsigned long SLEEP_TIME = 10000; // Sleep time between reads (in milliseconds)

BH1750 lightSensor;
MySensor gw;
MyMessage msg(CHILD_ID_LIGHT, V_LIGHT_LEVEL);
uint16_t lastlux;

void setup()  
{ 
  gw.begin();

  // Send the sketch version information to the gateway and Controller
  gw.sendSketchInfo("Light Lux Sensor", "1.1");

  // Register all sensors to gateway (they will be created as child devices)
  gw.present(CHILD_ID_LIGHT, S_LIGHT_LEVEL);

  lightSensor.begin();
}

void loop()      
{     
  lightSensor.configure(BH1750_ONE_TIME_LOW_RES_MODE);
  uint16_t lux = lightSensor.readLightLevel();// Get Lux value
  Serial.print("Lux: ");
  Serial.println(lux);
  if (lux > (lastlux + LIGHT_SENSOR_LUX_THRESHOLD)) {
      gw.send(msg.set(lux));
      lastlux = lux;
  }
  if (lux < (lastlux - LIGHT_SENSOR_LUX_THRESHOLD)) {
      gw.send(msg.set(lux));
      lastlux = lux;
  }

  // Power down the radio. Note that the radio will get powered back up
  // on the next write() call.
  gw.sleep(SLEEP_TIME); 
}

With some changes, this mySensor Lux node will run 2.22 Years. Please check my YouTube Sessions: https://www.youtube.com/playlist?list=PLYPTUTcLMTK4X3rSrr3FChxNeVwrH1Kmh